Labor social services spokeswoman Linda Burney said there was no way the opposition would support the "punitive, unworkable" policy.

With Labor and the Greens opposed to the plan, the government will need support from the Senate crossbench, and experts are pleading with them to reject the proposal.

Labor is also opposed to the government's desires to roll out cashless welfare cards nationally.

The coalition is yet to reveal draft laws to that end, but Government Services Minister Stuart Robert introduced legislation to the lower house on Wednesday to extend trials of the card in existing areas for another year until June 2021.

The draft laws also give effect to cashless debit card trials across the Northern Territory and in Cape York, to begin April next year.

The cashless welfare cards quarantine 80 per cent of payments so the money can only be spent on essential items.

Ms Burney said the technology should only be expanded on a case-by-case basis, describing the evaluation of existing trials as "quite inadequate".

"If a community has proper consultation and proper consent, and that community wants the cards, then Labor would not stand in the way," she told ABC radio.